Featured Research

from universities, journals, and other organizations

Galaxy growth spurts explained: Young galaxies can grow by sucking in cool gas

Date:

October 14, 2010

Source:

ESO

Summary:

New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics.

Share This

This artist's impression shows a young galaxy, about two billion years after the Big Bang, accreting material from the surrounding hydrogen and helium gas and forming many young stars. New results from ESO's Very Large Telescope have provided the first direct evidence that the accretion of pristine gas alone, without the need for violent major mergers, can fuel vigorous star formation and the growth of massive galaxies in the young universe.

Credit: ESO/L. Calçada

The first galaxies formed before the Universe was less than one billion years old and were much smaller than the giant systems -- including the Milky Way -- that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed.

Related Articles

A European team of astronomers has used ESO's Very Large Telescope to test this very different idea -- that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways -- by merging with other galaxies or by accreting material.

The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written.

The group began by selecting three very distant galaxies to see if they could find evidence of the flow of pristine gas from the surrounding space and the associated formation of new stars. They were very careful to make sure that their specimen galaxies had not been disturbed by interactions with other galaxies. The selected galaxies were very regular, smoothly rotating discs, similar to the Milky Way, and they were seen about two billion years after the Big Bang (at a redshift of around three).

In galaxies in the modern Universe the heavy elements [1] are more abundant close to the centre. But when Cresci's team mapped their selected distant galaxies with the SINFONI spectrograph on the VLT [2] they were excited to see that in all three cases there was a patch of the galaxy, close to the centre, with fewer heavy elements, but hosting vigorously forming stars, suggesting that the material to fuel the star formation was coming from the surrounding pristine gas that is low in heavy elements. This was the smoking gun that provided the best evidence yet of young galaxies accreting primitive gas and using it to form new generations of stars.

As Cresci concludes: "This study has only been possible because of the outstanding performance of the SINFONI instrument on the VLT. It has opened a new window for studying the chemical properties of very distant galaxies. SINFONI provides information not only in two spatial dimensions, but also in a third, spectral dimension, which allows us to see the internal motions inside galaxies and study the chemical composition of the interstellar gas."

[1] The gas filling the early Universe was almost all hydrogen and helium. The first generations of stars processed this primitive material to create heavier elements such as oxygen, nitrogen and carbon by nuclear fusion. When this material was subsequently spewed back into space by intense particle winds from massive young stars and supernova explosions the amounts of heavy elements in the galaxy gradually increased. Astronomers refer to elements other than hydrogen and helium as "heavy elements."

[2] By carefully splitting up the faint light coming from a galaxy into its component colours using powerful telescopes and spectrographs, astronomers can identify the fingerprints of different chemicals in remote galaxies, and measure the amounts of heavy elements present. With the SINFONI instrument on the VLT astronomers can go one better and get a separate spectrum for each part of an object. This allows them to make a map that shows the quantity of heavy elements present in different parts of a galaxy and also determine where in the galaxy star formation is occurring most vigorously.

Story Source:

The above story is based on materials provided by ESO. Note: Materials may be edited for content and length.

More From ScienceDaily

More Space & Time News

Featured Research

Mar. 3, 2015 — Meteorologists sometimes struggle to accurately predict the weather here on Earth, but now we can find out how cloudy it is on planets outside our solar system, thanks to new ... full story

Mar. 3, 2015 — Recent research contributes to the effort to determine the nature of dark matter, one of the most important mysteries in physics. As indirect evidence provided by its gravitational effects, dark ... full story

Mar. 2, 2015 — Dust plays an extremely important role in the universe -- both in the formation of planets and new stars. But the earliest galaxies had no dust, only gas. Now an international team of astronomers has ... full story

Mar. 2, 2015 — NASA's Dawn spacecraft has returned new images captured on approach to its historic orbit insertion at the dwarf planet Ceres. Dawn will be the first mission to successfully visit a dwarf planet when ... full story

Mar. 2, 2015 — An international team of researchers has demonstrated a way to assess the quality of water on Earth from space by using satellite technology that can visualize pollution levels otherwise invisible to ... full story

Feb. 27, 2015 — A new type of methane-based, oxygen-free life form that can metabolize and reproduce similar to life on Earth has been modeled. It is theorized to have a cell membrane, composed of small organic ... full story

Feb. 27, 2015 — Astronomers using data from NASA's Wide-field Infrared Survey Explorer, or WISE, have found a cluster of stars forming at the very edge of our Milky Way galaxy. This is the first time astronomers ... full story

Feb. 26, 2015 — If you put a camera in the ice machine and watched water turn into ice, the process would look simple. But the mechanism behind liquids turning to solids is actually quite complex, and understanding ... full story

Feb. 26, 2015 — Like a cowboy at a rodeo, NASA's newest Earth-observing satellite, the Soil Moisture Active Passive (SMAP), has triumphantly raised its "arm" and unfurled a huge golden "lasso" (antenna) that it will ... full story

NASA EDGE: SMAP Launch

NASA (Mar. 2, 2015) — Join NASA EDGE as they cover the launch of the Soil Moisture Active Passive (SMAP) spacecraft live from Vandenberg Air Force Base. Special guests include NASA Administrator Charlie Bolden, SMAP Project System Engineer Shawn Goodman and Lt Col Brande Walton and Joseph Sims from the Air Force. No word on the Co-Host&apos;s whereabouts.
Video provided by NASA

Related Stories

Nov. 13, 2014 — Astronomers have provided the first direct evidence that an intergalactic 'wind' is stripping galaxies of star-forming gas as they fall into clusters of galaxies. The observations help ... full story

July 5, 2013 — Astronomers have spotted a distant galaxy hungrily snacking on nearby gas. Gas is seen to fall inwards towards the galaxy, creating a flow that both fuels star formation and drives the galaxy's ... full story

Nov. 2, 2011 — Astronomers have used the light of a distant gamma-ray burst as a probe to study the make-up of very distant galaxies. The new observations, made with ESO's Very Large Telescope, have revealed ... full story

Mar. 9, 2011 — Astronomers have discovered and measured the distance to the most remote mature cluster of galaxies yet found. Although this cluster is seen when the universe was less than one quarter of its current ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.